Development of Ceramic Thermoelectric Oxides for Generator

Abstract:

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In this work we describe (i) the fabrication of thermoelectric modules based on oxide
bulk and foam materials of Ca3Co4O9 and Ca0.95Sm0.05MnO3(ii) and the metal to ceramic contacts
preparation. The open porous foam structures of thermoelectric materials can result in designing
efficient thermoelectric modules for waste heat sources involving gaseous and liquid media. The
possibility of direct large area physical contact of thermoelectric foam elements with hot media will
make them efficient electric power generators. The open porous thermoelectric materials with holes
can be a good candidate to confine phonons (lattice vibrations) in order to reduce the thermal
conductivity if the pores can be made sufficiently small. The performances of the modules were
evaluated and possible factors limiting their theoretical performance are discussed. A parameter
representing the quality of the modules termed as manufacturing factor (MF) representing the
cumulative effect of various factors involved in the fabrication process is introduced and evaluated
for the modules and compared to the reported modules.

Abstract: Foam replication method is capable of producing foams with a highly porous structure with adjustable pore dimension, shape and size. In this work, this method has been used to prepare stainless steel 316L foam and sintered at 1200°C, 1250°C and 1300°C in a vacuum furnace. The microstructure and elemental analysis of the sample were examined using scanning electron microscope (SEM) and Energy Dispersive X–Ray (EDX), while the mechanical properties of the samples was determined by using compression test. It was found that the average pore size was in the range of 330µm-350µm. The yield strength and elastic modulus are in the range of 58-66 GPa and 0.46-0.50GPa respectively.

Abstract: In this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0≤x≤0.3, 0≤y≤0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15–300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25×10-5, 5.3×10-6, 8.6×10-5 and 9×10-6 for sintered powders from undoped, Ni and B doped powders, respectively.